Nationalist rebel forces organizing and training in Sevilla, Spain, early in Spanish Civil War. Troops riding through the city in open transport vehicles. Troops marching with rifles in in front of the equestrian Statue at the Plaza Nueva Sevilla. A group of soldiers trains with field artillery. New recruits are organized. Commanding General of Sevilla, Gonzalo Queipo de Llanol, meets with other rebel leaders.

Army of Nationalist Spain attacks Spain Republic troops in Madrid, Spain. View over desert showing troops firing machine guns and rifles behind low ditches. Smoke rises as a result of an explosion. Troops march and parade on streets in the city of Madrid, Spain.

Destruction caused during Spanish Civil War in Spain. Buildings and churches seen alongside a bridge in Spain. Bomb wrecked buildings and churches. Heaps of debris seen. Spanish civilians fires rifles, including both men and women soldiers or combatants. Crowds gathered in streets during a demonstration. Dirty and ragged refugee families living in caves after destruction of their towns and villages by war. Children eating in caves. Photograph of Francisco Franco, Dictator and Head of State of Spain. Aerial views of German aircraft of the Condor Legion seen in flight, including Stuka dive bombers, Junkers JU 52 transports, and a Heinkel He-111 E taking off. X symbol of Condor Legion aircraft seen on tails of some of the aircraft. Some bi-planes are also seen as they taxi on an airfield with German pilots or crew nearby.

Opening scene shows Spanish labor Union supporters marching in Valencia, Spain, in 1936, under a large banner with initals C.N.T and A.I.T. printed on its top corners (Standing for Confederación Nacional del Trabajo (CNT) and Asociación Internacional de los Trabajadores (AIT), respectively. The word: "Authores" (Authors) appears in large print on the banner. One marcher carries a large Spanish 2nd Republic flag with letters "A.I.T." on it. Next, closeups of uniformed band members playing instruments, are seen. Persons standing nearby raise their right fists in support of the Republican anti-fascist movement. Closeups of band musicians playing.

Film opens showing Catalan volunteers during the advent of the Spanish Civil War, standing in front of a statue dedicated to Catalan Volunteers who had fallen in World War I. (It is a larger-than-life bronze statue of a nude male figure with arms upraised, created by Catalan sculptor Josep Clarà. It stands in the Parc de la Ciutadella in Barcelona. It was dedicated on July 14, 1936.) Camera pans across the group, some in military uniforms, and others in mufti. Scene shifts to a street in Valencia, Spain, where men in business attire surround a man standing at a microphone, speaking. The general scene is festive, with flags and banners seen in places and people dressed in their best. "Plaza de la Generalitat Catalana" is written across a building front, identifying the location. View shifts to large well-dressed crowd, applauding the speaker. Closeup of the principal speaker and two companions at the microphone. Next, a large uniformed band of musicians is seen being conducted and playing for the crowd. Angled closeup of the band director. Another uniformed music director leads the crowd in a patriotic song. Some boy scouts are see participating. A troop of Boy Scouts, some shouldering rifles, march to accompanyment of a Boy Scout drum corps. View changes to men informally gathered around a large round structure. They smoke and socialize. Scene shifts to Parc de la Ciutadella in Barcelona, where spectators watch as a man places a huge bouquet of flowers on the ground in front of the statue dedicated to the fallen Catalan Volunteers of World War 1. View of statue silhouetted against the sky. Camera pans down the statue.

Documentary titled the 'Rehearsal of War' depicts the Spanish Civil War and preparations of fascist powers in Europe. Bombing and combat during the civil war and the wounded carried for treatment. The U.S. Chief of Staff General Craig at his office in Washington DC with his aides evaluates the tactics and strategies involved in the civil war. Italian dictator Benito Mussolini and German dictator Adolf Hitler with aides address large crowds. Advanced war machinery developed by these fascist nations. Tanks and flamethrowers with infantry in a practice range. U.S. military experts discuss reports of the Spanish war in their office. U.S. ambassador in Spain confers on telephone and gives daily report of the war in Spain. A French navy ship near the coast of Spanish war front also reports about the war.